This invention relates to pneumatic tire cover having a radial carcase, i.e. a carcase formed by one or more plies whose threads (cords) lie in meridian planes passing through the axis of rotation of the tire or form small angles with said planes. It is known that said tires beside the radial carcase, contain a circumferential peripheral structure which extends between the tire tread and the carcase, said structure aiming at making the tire less deformable, limiting its dragging against the ground.
The combination of the radial carcase and the circumferential structure has proved to be very advantageous because beside a long tread life, it allows an excellent comfort for driving due to the great flexibility of the sides of the tire or, equivalently, to the low rigidity of the carcase.
Said flexibility of the sides does have, however, some negative aspects given that the sides provide only very weak transverse reinforcement when the tire is stressed by forces in the direction of the axis of rotation.
Said forces arise, for example, in bends when a centrifugal force develops, acting on the centre of gravity of the vehicle.
Furthermore, the accentuated flexibility of the sides makes the strength of the tire critical in the region of the beads and, more particularly, in the region of the connection between the extremely pliable sides and the beads, which bear on the lateral projections of the mounting rim.
These inconveniences are particularly relevant in the case of tires for industrial motor vehicles because of the high stresses to which they are subject.
As it is known, it is possible nowadays to manufacture tires of this kind with only one carcase ply, by means of the use of fabrics with steel cords having very high values of unitary strength.
The use of such fabrics with steel cords, together with other reinforcements in the same material, gives satisfactory solutions of the problems regarding tires for industrial motor vehicles.
Recently new synthetic fabric materials have been prepared such as aromatic polyamides (for example the product known under the trade name "Kevlar") which, as well as having a strength per unit of cross sectional area very near to that of steel, possess an improved resistance to fatigue, render easier and therefore less costly the cutting and preparation of the partly finished product in general, and by reducing the weight of the tire increase indirectly the driving comfort by a reduction of the so-called "unsprung weight" of the vehicle. The introduction of such materials as reinforcements in tires has however again raised the problem regarding wear in the region of the beads, previously considered, together with the problem of the lateral stability of the vehicle.